1. Technical Field
The present disclosure relates to a contact lens material, and more particularly, to a method for manufacturing a hydrophilic silicone macromer used in a contact lens.
2. Description of Related Art
Silicone hydrogel has long been considered as one of contact lens materials because of its high oxygen permeability. Silicone hydrogel lens can deliver a sufficient amount of oxygen to a cornea, and thus is suitable for long-time wearing and less likely to cause eye complications.
The composition of a silicone hydrogel contact lens typically contains one or more kinds of silicone-based monomers, macromers and prepolymers. A silicone monomer usually has at most 4 silicon atoms, and its molecular weight typically is less than 500 daltons, such as 3-(methacryloyloxypropyl)-tris(trimethylsiloxy)silane (TRIS). A silicone macromer has linear siloxane units and an ethylenically unsaturated polymerizable group, and its molecular weight usually is higher than 500 daltons. A silicone prepolymer has linear siloxane units and two ethylenically unsaturated polymerizable groups. Silicones are highly hydrophobic material, and how to enhance the wettability of a silicone hydrogel lens becomes a challenge.
There are some methods for improving the wettability of a silicone hydrogel lens, such as performing a plasma process on the surface of the silicone-containing hydrophobic lens, adding hydrophilic polymers such as polyvinylpyrrolidone to a silicone hydrogel composition, or using a silicone-based prepolymer having polyethylene oxide side chains. Keogh et al. (the U.S. Pat. No. 4,259,467) disclosed structures of hydrophilic silicone-based monomers, macromers and prepolymers; however, no effective method for manufacturing a hydrophilic silicone macromer has ever been disclosed especially for those containing amide or phosphoryl choline hydrophilic side chains.
Therefore, there is a need for an effective method for manufacturing hydrophilic silicone macromer and the macromer made therefrom to solve the problems in the art.